Thermal-Fluid Systems ME303

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The objective of this session is to introduce the subject of software engineering. When you have read this session you will understand what software engineering is and why it is important, know the answers to key questions which provide an introduction to software engineering, understand ethical and professional issues which are important for software engineers.

Introduction

Virtually all countries now depend on complex computer-based systems. More and more products incorporate computers and controlling software in some form. The software in these systems represents a large and increasing proportion of the total system costs. Therefore, producing software in a cost-effective way is essential for the functioning of national and international economies.

Software engineering is an engineering discipline whose goal is the cost-effective development of software systems. Software is abstract and intangible. It is not constrained by materials, governed by physical laws or by manufacturing processes. In some ways, this simplifies software engineering as there are no physical limitations on the potential of software. In other ways, however, this lack of natural constraints means that software can easily become extremely complex and hence very difficult to understand.

Software engineering is still a relatively young discipline. The notion of ‘software engineering’ was first proposed in 1968 at a conference held to discuss what was then called the ‘software crisis’. This software crisis resulted directly from the introduction of powerful, third generation computer hardware. Their power made hitherto unrealisable computer applications a feasible proposition. The resulting software was orders of magnitude larger and more complex than previous software systems.

Early experience in building these systems showed that an informal approach to software development was not good enough. Major projects were sometimes years late. They cost much more than originally predicted, were unreliable, difficult to maintain and performed poorly. Software development was in crisis. Hardware costs were tumbling whilst software costs were rising rapidly. New techniques and methods were needed to control the complexity inherent in large software systems.

These techniques have become part of software engineering and are now widely although not universally used. However, there are still problems in producing complex software which meets user expectations, is delivered on time and to budget. Many software projects still have problems and this has led to some commentators (Pressman, 1997) suggesting that software engineering is in a state of chronic affliction.

As our ability to produce software has increased so too has the complexity of the software systems required. New technologies resulting from the convergence of computers and communication systems place new demands on software engineers. For this reason and because many companies do not apply software engineering techniques effectively, we still have problems. Things are not as bad as the doomsayers suggest but there is clearly room for improvement.


This course deals with the transfer of work, energy, and material via gases and liquids. These fluids may undergo changes in temperature, pressure, density, and chemical composition during the transfer process and may act on or be acted on by external systems. You must fully understand these processes if you are an engineer working to analyze, troubleshoot, or improve existing processes and/or innovate and design new ones.

In your everyday life, you will likely encounter examples of the thermal-fluid systems we will study in this course. Consider the following scenarios:

1. Read this recent report by Gary Goettling for the Georgia Tech Alumni Association.* In it, Goettling describes a refrigeration system with no moving parts based on improvements to a patent filed by Einstein and Szilard in 1930. As an engineer, how would you go about evaluating this design for energy efficiency, safety, reliability, and manufacturing, operating, and installation costs?

2. Have you ever wondered how the level sensor on a retail gasoline dispenser automatically shuts off when the gasoline tank in an automobile is full?

3. Have you ever been tempted to share your opinion concerning the debates about global climate change? Global climate involves consideration of radiation, convection, and chemical change amongst many other factors.

4. Have you wondered how it is possible to estimate the composition and flow rate of a mixture of petroleum, water, and natural gas at a remote location five miles under the ocean surface.

5. Just how dirty do your air filters need to be in your domestic air handling system or on your motor vehicle for it to be economically advantageous to replace them?

Quiz PDF eBook: 
Thermal-Fluid Systems ME303
Download Thermal-Fluid Systems Quiz PDF eBook
33 Pages
2014
English US
Educational Materials



Sample Questions from the Thermal-Fluid Systems ME303 Quiz

Question: A countercurrent heat exchanger operates with the following temperatures: cold fluid inlet 15°C, cold fluid outlet 25°C, hot fluid inlet 90°C, and hot fluid outlet 30°C. Calculate the logarithmic-mean temperature difference in °C.

Choices:

45°C

30°C

27°C

25°C

50°C

Question: A countercurrent heat exchanger operates with the following temperatures: cold fluid inlet 20°C, hot fluid inlet 90°C. The heat capacity of the hot fluid is 2.2 kJ/kg K. The heat capacity of the cold fluid is 1 kJ/kg K. The flow rate of the hot fluid is 5 kg/s. The flow rate of the cold fluid is 66 kg/s. The area for heat transfer is 10 m[sup]2[/sup]. The overall heat transfer coefficient is 2418 W/m[sup]2[/sup] K. What are the outlet temperatures?

Choices:

T[sub]hoto[/sub] = 29.6° C, T[sub]coldo[/sub] = 30.1°C

T[sub]hoto[/sub] = 29.6° C, T[sub]coldo[/sub] = 40.1°C

T[sub]hoto[/sub] = 29.6 °C, T[sub]coldo[/sub] = 50.1°C

T[sub]hoto[/sub] = 19.6° C, T[sub]coldo[/sub] = 20.1°C

T[sub]hoto[/sub] = 39.6 °C, T[sub]coldo[/sub] = 30.1°C

Question: Find the Carnot coefficient of performance for a refrigeration system operating between 320°K and 285°K.

Choices:

6.5

8.14

0.12

0.16

3.0

Question: A fluid with heat capacity 2.2 kJ/kg K enters a heat exchanger at 90°C and leaves at 30°C at a flow rate of 5 kg/s. Calculate the heat removal from this fluid.

Choices:

660 W

6.60 kW

66.0 kW

660 kW

66.0 W

Question: A reciprocating, spark ignition engine takes in an air-fuel mixture at 20°C. It has a compression ratio of 12. The air-to-fuel ratio is 14, and the heating value of the fuel is 70,000 kJ/kg. For an air standard cycle analysis, what is the highest temperature reached in °K? You may assume C[sub]v[/sub] is approximately 0.7 kJ/kg K and that k=C[sub]p[/sub]/C[sub]v[/sub] = 1.4.

Choices:

7934°K

791°K

5934°K

591°K

1243°K

Question: A refrigeration system with a COP of 3.5 is used to make ice from water at 0°C at a rate of 1000 lbs per day. What is the minimum power required by the refrigerator?

Choices:

100 W

200 W

1000 W

500 W

5000 W

Question: For a vapor-compression refrigeration system, the enthalpy of the refrigerant at the evaporator input is 88 kJ/kg; the enthalpy at the compressor input is 190 kJ/kg; the enthalpy at the compressor output is 260 kJ/kg. The compression is isenthalpic. What is the coefficient of performance of the system?

Choices:

1.0

2.0

1.5

0.66

3.0

Question: If ΔT[sub]lm[/sub] = 27°C, Q = 660 kW, and A = 10 m[sup]2[/sup] for a countercurrent heat exchanger, what is the overall heat transfer coefficient in W/m[sup]2[/sup] K?

Choices:

24W/m[sup]2[/sup] K

242W/m[sup]2[/sup] K

2418W/m[sup]2[/sup] K

24180W/m[sup]2[/sup] K

2.4W/m[sup]2[/sup] K

Question: A fluid with heat capacity 2.2 kJ/kg K enters a heat exchanger at 90°C and leaves at 30°C at a flow rate of 5 kg/s. If the heat capacity of the cooling fluid for the heat exchanger is 1 kJ/kg K, what is its flow rate in kg/s?

Choices:

66 g/s

6.6 kg/s

66 kg/min

660 kg/s

66 kg/s

Question: Combustion of a fuel at 1200°K at a rate of 3 kW produces steam at 550°K.The steam then produces 2 kW of work and rejects some heat to 310°K. What is the second-law efficiency of the process?

Choices:

66%

74%

39%

89%

100%

Question: Calculate the maximum COP for a vapor absorption refrigeration system operating with a heat source (generator) at 110°C, a chiller temperature (absorber) of 5°C, and a condenser temperature of 30°C.

Choices:

0.5

1.9

2.1

0.43

2.3

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Source:  Dr. Steve Gibbs. Thermal-Fluid Systems. The Saylor Academy 2014, http://www.saylor.org/courses/me303/
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